Mesopotamia, in "the cradle of civilization", offers us the ancient
Epic of Galgamesh, probably first composed around 2000 BC.
In this ancient Sumerian story,
Gilgamesh, king of Uruk, sets out on a quest for immortality to the
Garden of the Sun, the land of everlasting life.
To reach it, Gilgamesh must pass through the Sun's gate in
the mountain of the horizon.
The setting Sun disappears there and emerges from it at sunrise.
A pair of terrifying scorpion-peole stationed at the gate
of heaven guard the Sun's path. But eventually Gilgamesh
gains entrance to the next level.

E. C. Krupp postulates:
"Around the 17th century BC., Mesopotamian boundary stones began to
carry astronomical symbols, including that of the terrifying
scorpion-man... Some scholars identify this creature as the
Mesopotamian antecedent of Sagittarius, the Archer.
Although no one is sure that the boundary stone
scorpion-man is also meant to be the Sun's bodyguard at the gate of
heaven, the constellation could have evolved from the earlier imagery
through its asssociation with the Milky Way.
In the second millennium B.C., when the stars of Capricornus hosted the
winter-solstice Sun, Sagittarius could have been posted as the advance
guard at the crossroads of the Sun's path and the Milky Way."

Legend described by E. C. Krupp
in Sky and Telescope, September 1997. pp. 80-81.